M. Millán

The applications of optical correlation techniques to the remote sensing of SO2 plumes using sky light

Abstract A correlation spectrometer for the passive remote sensing of sulphur dioxide in stack plumes is described and the theoretical response of the sensor is developed including the effect of atmospheric scattering. Initital results of field tests are presented and sources of error are discussed in some detail. Experience to date indicates that good accuracy can be realized for stable undistorted plumes when atmospheric scattering and geometry of the measurement are taken fully into account.

Remote sensing of air pollutants. A study of some atmospheric scattering effects

A simple radiation transfer model has been developed to investigate the effects of atmospheric scattering on the passive spectroscopic remote sensing of pollutants. The problems of remote SO2 measurement at stack tops, under a uniformly mixed layer, and under elevated plumes are addressed using the response function of a correlation spectrometer. The effect of various atmospheric meteorological ranges and intermittent condensation in elevated plumes have also been examined.

Remote sensing of air pollutants by correlation spectroscopy--instrumental response characteristics.

Abstract The philosophy behind the development of the correlation spectroscopic techniques now in use for the remote sensing of air pollutants is briefly examined. In order to focus attention on the operational characteristics common to most of these, dispersive as well as non-dispersive, -sensors, the authors select one of the commercially available instruments to describe in certain detail how the instrumental design parameters, the available backgrounds or sources and the geometry of the observation interact to affect the output signal. This work is intended to review the development of the selected instrumental technique, and also to alert the user about some factors which must be considered both with the gathering and during the analysis of the data collected with these types of sensors.

The application of correlation spectroscopy to the study of dispersion from tall stacks

Vertically-integrated SO2 cross-sections of the plume from a tall stack have been obtained with a dispersive correlation spectrometer. A methodology is described for processing these remotelysensed data to determine plume boundaries, horizontal dispersion coefficients and ground path. In addition, the cross-sections are combined to yield some insight into the diffusion process affecting the plume and this information is used to establish the conditions under which calculations of mass flow can be made.

Detection of a plume 400 km from the source

Abstract An unexpected SO 2 reading over the northern edge of Toronto, Canada, by means of a COSPEC remote sensor, and the posterior trajectory analysis of the air parcel over Toronto at the time of the measurement, indicate that the INCO Sudbury plume was observed at 400 km from its source. Some estimates of the mass flux in the plume and of its horizontal dimensions are presented.

Dispersive correlation spectroscopy: a study of mask optimization procedures.

A procedure has been established to obtain the design parameters of the masks used in dispersive correlation spectrometers. The SNR equations are used to derive the mask equations. These are later solved for some simplified band models, and the obtained parameters are used as the initial values in an iterative program which determines the final design parameters. The calculations can be performed for various backgrounds and instrumental line profiles in order to achieve the best compromise for the detection of pollutants, and other trace gases, in the atmosphere.

A note on the geometry of plume diffusion measurements

Abstract In plume diffusion studies, the researcher is often confronted with the problem of deciding how well his data represents actual instantaneous or average plume cross-sections. In particular, there are limits to the geometry of plume measurements beyond which commonly used techniques for the projection of profiles yield unrealistic results. This note proposes a projection scheme, and criteria for various transect geometries, such that the derived plume profiles do not deviate from the actual profile beyond acceptable limits.